1. Field of the Invention
The present invention relates in general to ac silane coupling agent and a method for the preparing the same by which an organic material and an inorganic material can be covalently bonded to each other. More particularly, the present invention relates to a silane coupling agent useful for the preparation of a composite material of a silicone oxide and an alcohol group-containing polymer, such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, tetrafluoroethylene-vinylalcohol copolymer, or poly(vinylbutyral-vinylalcohol-vinylacetate) copolymer.
2. Description of the Prior Art
A silane coupling agent has a trialkoxysilyl group and an organic functional group which is an acetal or dioxoranyl group. The trialkoxysilyl group is reacted with silanol present in the surface of an inorganic material, such as silicate, whereas the acetal or dioxiranyl group is reacted with a hydroxy group which is a functional group of an organic material. Consequently, they serve to connect the organic material and the inorganic material to each other.
In a composite inorganic-organic material, the most problematic factor is the compatibility between the organic material and the inorganic material. Where such a compatibility is insufficient, the phase separation between the organic and inorganic materials occurs, thus deteriorating physical properties of the composite material.
Meanwhile, in the composite material of the organic material and the inorganic material, the compatibility can be enhanced when the two materials are bonded by a hydrogen bond or other chemical bond. However, the composite material can not be enhanced in a moisture barrier property by only the hydrogen bond.
U.S. Pat. Nos. 5,604,042 and 5,512,338, to which the present invention is related, describes coating the surface of a polyurethane, polyethylene or polyethylene terephtalate film with a solution containing polyvinyl alcohol reacted with melamine-formaldehyde, thereby enhancing an oxygen barrier property of the resulting film structure. Moreover, to improve the moisture barrier property of the film structure, the solution-coated surface is adhered with a cellulose or polyvinylidene chloride film.
In addition, U.S. Pat. Nos. 5,547,764, 5,496,649, 4,416,938, and 4,262,067 describe crosslinking a hydroxy group in polyvinyl alcohol with aldehyde using glyoxal, or glutaric dialdehyde, thereby improving the oxygen barrier property of the resulting film structure. In this case, even if the hydroxy group in polyvinyl alcohol is reacted with aldehyde to form an acetal group, the formed acetal group can serve as a coupling agent between polyvinyl alcohol polymer chains.
Furthermore, PCT Publication WO 94/07947 describes reacting tetraalkoxysilane with polyvinyl alcohol in the presence of formic acid to form a Sixe2x80x94Oxe2x80x94Si bond and also to couple the hydroxy group with the formic acid, thereby improving toughness. However, the latter reference describes that a Sixe2x80x94Oxe2x80x94C bond is not formed in the reaction of tetraalkoxysilane and polyvinyl alcohol, and polyvinyl alcohol is dispersed in tetraalkoxysilane. That is to say, the resultant product is not a composite organic-inorganic material, but consists of an organic material dispersed in the inorganic material. Where such a mixture is allowed; to be stand in water for an extended period of time, a fine phase separation between the organic material and the inorganic material may occur in the mixture, thereby deteriorating physical properties of the mixture.
It is an object of the present invention to improve the compatibility, that is a basic problem with the composite organic-inorganic material, and to prepare a silane coupling agent containing an organic functional group, which is an acetal group or a dioxoranyl group, by reacting a vinyl derivative with an alkoxysilane derivative, or by reacting alkylmagnesium halide with haloalkoxysilane.
A silane coupling agent in accordance with the present invention is prepared by one of the following two methods. A first method comprises the steps of dissolving a vinyl derivative represented by the following formula II in an organic solvent under a nitrogen or argon atmosphere, and reacting the resulting solution with an alkoxysilane derivative represented by the following formula III in the presence of a metal catalyst to produce a silane coupling agent represented by the following formula I. A second method comprises the steps of dissolving alkyl magnesium. halide represented by the following formula IV in a solvent under a nitrogen or argon atmosphere, and reacting the resulting solution with haloalkoxysilane represented by the following formula V to produce a silane coupling agent represented by the following formula I:
R1R2R3Sixe2x80x94Xxe2x80x83xe2x80x83(I)
xe2x80x83Xxe2x80x94MgZxe2x80x83xe2x80x83(III)
R1R2R3Sixe2x80x94Zxe2x80x83xe2x80x83(IV)
Hxe2x80x94SiR1R2R3xe2x80x83xe2x80x83(V)
wherein R1, R2, and R3, respectively, represent straight or branched alkyl having 4 to 22 carbon atoms, alkoxy, phenyl, phenylalkoxy, benzyloxy or phenylalkyl group, each of these groups being optionally substituted with a functional group, such as fluoride, glycidyloxy, amine, vinyl, (meth)acetyl, amino or mercapto group, with the proviso that at least one of R1, R2, and R3 contain an alkoxy group;
X is an alkyl or aryl alkyl group having 4 to 22 carbon atoms, each of these groups being substituted with at least one functional group selected from dioxoranyl, dioxanylalkyl, ketal, alkylideneketal, cycloalkylidenekatal, acetal, dialkylacetal, alkylideneacetal, phenylalkylideneacetal, benzylideneacetal, ketone, and cycloacetal having 4 to 8 carbon atoms and optionally containing, in its carbon chain, at least one atom selected from oxygen, sulfur and nitrogen;
Y1 is an alkyl or arylalkyl group having 4 to 19 carbon atoms, each of these groups being substituted with at least one functional group selected from dioxoranylalkyl, dioxanylalkyl, ketal, acetal, dialkylacetyl, alkylideneacetal, phenylalkylideneacetal, benzylideneacetal, ketone, aldehyde and cycloacetal having 4 to 8 carbon atoms and optionally containing, in its carbon chain, at least one atom selected from oxygen, sulfur and nitrogen;
Y2 has a definition identical to that of Y1, or may contain hydrogen atom; and
Z is selected from F, Cl, Br, and I.
The metal catalyst used in accordance with the method of the present invention includes a complex compound in which a central metal is Pt, Ir, Os, Au, or As, and a ligand is H, F, Cl, Br, I, PPh3, C5H5, CO, OH, C2H4, CH3, PCH3, Si(CH3)3, C5H4(CH3), C5H3(CH3)2, C5(CH3)5, 1,5-cyclooctadiene, norbornadiene, C6H5, CH2-t-Bu, acetylacetonato and a combination of two or more of these compounds.